Not passing default matplotlib parameters to backends (all known kwargs were being passed, now only the ones provided by the user)

Author: Marc Garcia

pandas/plotting/_core.py

@@ -511,7 +511,7 @@ def __init__(self, data):
         self._parent = data
 
     @staticmethod
-    def _get_call_args(data, args, kwargs):
+    def _get_call_args(backend_name, data, args, kwargs):
         """
         This function makes calls to this accessor `__call__` method compatible
         with the previous `SeriesPlotMethods.__call__` and
@@ -542,9 +542,9 @@ def _get_call_args(data, args, kwargs):
                 ('yerr', None), ('xerr', None), ('secondary_y', False),
                 ('sort_columns', False)]
         else:
-            return TypeError(('Called plot accessor for type {}, expected '
-                              'Series or DataFrame').format(
-                                  type(data).__name__))
+            raise TypeError(('Called plot accessor for type {}, expected '
+                             'Series or DataFrame').format(
+                                 type(data).__name__))
 
         if args and isinstance(data, ABCSeries):
             msg = ('`Series.plot()` should not be called with positional '
@@ -559,21 +559,26 @@ def _get_call_args(data, args, kwargs):
                           FutureWarning, stacklevel=3)
 
         pos_args = {name: value for value, (name, _) in zip(args, arg_def)}
-        kwargs = dict(arg_def, **pos_args, **kwargs)
+        if backend_name == 'pandas.plotting._matplotlib':
+            kwargs = dict(arg_def, **pos_args, **kwargs)
+        else:
+            kwargs = dict(pos_args, **kwargs)
 
         x = kwargs.pop('x', None)
         y = kwargs.pop('y', None)
         kind = kwargs.pop('kind', 'line')
         return x, y, kind, kwargs
 
     def __call__(self, *args, **kwargs):
-        x, y, kind, kwargs = self._get_call_args(self._parent, args, kwargs)
+        plot_backend = _get_plot_backend()
+
+        x, y, kind, kwargs = self._get_call_args(plot_backend.__name__,
+                                                 self._parent, args, kwargs)
 
         kind = self._kind_aliases.get(kind, kind)
         if kind not in self._all_kinds:
             raise ValueError('{} is not a valid plot kind'.format(kind))
 
-        plot_backend = _get_plot_backend()
         # The original data structured can be transformed before passed to the
         # backend. For example, for DataFrame is common to set the index as the
         # `x` parameter, and return a Series with the parameter `y` as values.

pandas/tests/plotting/test_misc.py

@@ -31,6 +31,41 @@ def test_series_plot_with_positional_arguments_warns():
         Series([1, 2, 3]).plot('line', None)
 
 
+def test_get_accessor_args():
+    func = plotting._core.PlotAccessor._get_call_args
+
+    msg = 'Called plot accessor for type list, expected Series or DataFrame'
+    with pytest.raises(TypeError, match=msg):
+        func(backend_name='', data=[], args=[], kwargs={})
+
+    with tm.assert_produces_warning(FutureWarning,
+                                    check_stacklevel=False):
+        func(backend_name='', data=Series(), args=[''], kwargs={})
+
+    x, y, kind, kwargs = func(backend_name='', data=Series(),
+                              args=['line', None], kwargs={})
+    assert x is None
+    assert y is None
+    assert kind == 'line'
+    assert kwargs == {'ax': None}
+
+    x, y, kind, kwargs = func(backend_name='', data=DataFrame(),
+                              args=['x'], kwargs={'y': 'y',
+                                                  'kind': 'bar',
+                                                  'grid': False})
+    assert x == 'x'
+    assert y == 'y'
+    assert kind == 'bar'
+    assert kwargs == {'grid': False}
+
+    x, y, kind, kwargs = func(backend_name='pandas.plotting._matplotlib',
+                              data=Series(), args=[], kwargs={})
+    assert x is None
+    assert y is None
+    assert kind == 'line'
+    assert len(kwargs) == 22
+
+
 @td.skip_if_no_mpl
 class TestSeriesPlots(TestPlotBase):